Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2017 May 3
Explanation: No, hamburgers are not this big. What is pictured is a sharp telescopic view of a magnificent edge-on spiral galaxy NGC 3628, a puffy galactic disk divided by dark dust lanes. Of course, this deep galactic portrait puts some astronomers in mind of its popular moniker, The Hamburger Galaxy. The tantalizing island universe is about 100,000 light-years across and 35 million light-years away in the northern springtime constellation Leo. NGC 3628 shares its neighborhood in the local Universe with two other large spirals M65 and M66 in a grouping otherwise known as the Leo Triplet. Gravitational interactions with its cosmic neighbors are likely responsible for the extended flare and warp of this spiral’s disk.
Comet Halley’s 2 meteor showers
It’s because comets like Halley are so crumbly that we see annual meteor showers. One shower spawned by this comet is going on now. Another is visible in October.
Comet Halley, proud parent of two meteor showers, swings into the inner solar system about every 76 years. At such times, the sun’s heat causes the comet to loosen its icy grip over its mountain-sized conglomeration of ice, dust and gas. At each pass near the sun, the crumbly comet sheds a fresh trail of debris into its orbital stream. It lost about 1/1,000th of its mass during its last flyby in 1986. It’s because comets like Halley are so crumbly that we see annual meteor showers, like the Eta Aquarid meteor shower that’s going on now. Follow the links below to learn more about Comet Halley, the meteor showers it spawns, and about how astronomers calculate the velocities of meteors streaking across our sky.
Comet Halley’s 2 meteor showers. Because Comet Halley has circled the sun innumerable times over countless millennia, cometary fragments litter its orbit. That’s why the comet doesn’t need to be anywhere near the Earth or the sun in order to produce a meteor shower. Instead, whenever our Earth in its orbit intersects Comet Halley’s orbit, cometary bits and pieces – oftentimes no larger than grains of sand or granules of gravel – smash into Earth’s upper atmosphere, to vaporize as fiery streaks across our sky: meteors.
It so happens we intersect Comet Halley’s orbit not once, but twice each year. In early May, we see bits of this comet as the annual Eta Aquariid meteor shower.
Then some six months later, in October, Earth in its orbit again intersects the orbital path of Comet Halley. This time around, these broken-up chunks from Halley’s Comet burn up in Earth’s atmosphere as the annual Orionid meteor shower.
By the way, these small fragments are called meteoroids when in outer space, and meteors when they vaporize in the Earth’s atmosphere.
Meteors in annual showers – made from the icy debris of comets – don’t hit the ground. They vaporize high in Earth’s atmosphere. The more rocky or metallic asteroids are what sometimes hit the ground, and then they are called meteorites.
Where is Comet Halley now? Often, astronomers like to give distances of solar system objects in terms of astronomical units (AU), which is the sun-Earth distance. Comet Halley lodges 0.587 AU from the sun at its closest point to sun (perihelion) and 35.3 AU at its farthest point (aphelion).
In other words, Halley’s Comet resides about 60 times farther from the sun at its closest than it does at its farthest.
It was last at perihelion in 1986, and will again return to perihelion in 2061.
At present, Comet Halley lies outside the orbit of Neptune, and not far from its aphelion point. See the image at the top of this post – for May, 2017 – via Fourmilab.
Even so, meteroids swim throughout Comet Halley’s orbital stream, so each time Earth crosses the orbit of Halley’s Comet, in May and October, these meteoroids turn into incandescent meteors once they plunge into the Earth’s upper atmosphere.
Of course, Comet Halley isn’t the only comet that produces a major meteor shower …
|Meteor Shower||Parent Body||Semi-major axis||Orbital Period||Perihelion||Aphelion|
|Quadrantids||2003 EH1 (asteroid)||3.12 AU||5.52 years||1.19 AU||5.06 AU|
|Lyrids||Comet Thatcher||55.68 AU||415 years||0.92 AU||110 AU|
|Eta Aquarids||Comet 1/P Halley||17.8 AU||75.3 years||0.59 AU||35.3 AU|
|Delta Aquarids||Comet 96P/Machholz||3.03 AU||5.28 years||0.12 AU||5.94 AU|
|Perseids||Comet 109P/Swift-Tuttle||26.09 AU||133 years||0.96 AU||51.23 AU|
|Draconids||Comet 21P/Giacobini–Zinner||3.52 AU||6.62 years||1.04 AU||6.01 AU|
|Orionids||Comet 1/P Halley||17.8 AU||75.3 years||0.59 AU||35.3 AU|
|Taurids||Comet 2P/Encke||2.22 AU||3.30 years||0.33 AU||4.11 AU|
|Leonids||Comet 55P/Tempel-Tuttle||10.33 AU||33.22 years||0.98 AU||19.69 AU|
|Geminids||3200 Phaethon (asteroid)||1.27 AU||1.43 years||0.14 AU||2.40 AU|
How fast do meteors from Comet Halley travel? If we can figure how fast Comet Halley travels at the Earth’s distance from the sun, we should also be able to figure out how fast these meteors fly in our sky.
Some of you may know that a solar system body, such as a planet or comet, goes faster in its orbit as it nears the sun and more slowly in its orbit as it gets farther away. Halley’s Comet swings inside the orbit of Venus at perihelion – the comet’s nearest point to the sun. At aphelion – its most distant point – Halley’s Comet goes all the way beyond the orbit of Neptune, the solar system’s outermost (known) planet.
When the meteoroids from the orbital stream of Halley’s Comet streak across the sky as Eta Aquarid or Orionid meteors, we know these meteoroids/meteors have to be one astronomical unit (Earth’s distance) from the sun. It might be tempting to assume that these meteoroids at one astronomical unit from the sun travel through space at the same speed Earth does: 108,000 kilometers or 67,000 miles per hour.
However, the velocity of these meteoroids through space does not equal that of Earth at the Earth’s distance from the sun. For that to happen, Earth and Halley’s Comet would have to orbit the sun in the same period of time. But the orbital periods of Earth and Halley’s Comet are vastly different. Earth takes one year to orbit the sun whereas Halley’s Comet takes about 76 years.
However, thanks to the great genius, Isaac Newton, we can easily compute the velocity of these meteoroids/meteors at the Earth’s distance from the sun by using Isaac Newton’s Vis-viva equation, his poetic rendition of instantaneous motion.
The answer, giving the velocity of these meteoroids through space at the Earth’s distance from the sun, is virtually at our fingertips. All we need to know is Comet Halley’s semi-major axis (mean distance from the sun) in astronomical units. Here you have it:
Comet Halley’s semi-major axis = 17.8 astronomical units.
In the easy-to-use Vis-viva equation below, r = distance from sun in astronomical units, and a = semi-major axis of Comet Halley’s orbit in astronomical units. In other words, r = 1 AU and a = 17.8 AU.
Vis-viva equation (r = distance from sun = 1 AU; and a = semi-major axis = 17.8 AU):
Velocity = 67,000 x the square root of (2/r – 1/a)
Velocity = 67,000 x the square root of (2/1 – 1/17.8)
Velocity = 67,000 x the square root of (2 – 0.056)
Velocity = 67,000 x the square root of 1.944
Velocity = 67,000 x 1.39
Velocity = 93,130 miles per hour or 25.87 miles per second
The above answer gives the velocity of these meteoroids through space at the Earth’s distance from the sun. However, if these meteoroids were to hit Earth’s atmosphere head-on, that would push the velocity up to an incredible 160,130 miles per hour (93,130 + 67,000 = 160,130). NASA gives the velocity for the Eta Aquarid meteors and Orionid meteors at 148,000 miles per hour, which suggests the collision of these meteoroids/meteors with Earth is not all that far from head-on.
We can also use the Vis-viva equation to find out the velocity of Halley’s Comet (or its meteoroids) at the perihelion distance of 0.59 AU and aphelion distance of 35.3 AU.
Perihelion velocity = 122,331 miles per hour
Aphelion velocity = 1,464 miles per hour
Bottom line: Halley’s Comet spawned two annual meteor showers, the Eta Aquarids in May and the Orionids in October. Plus … where the comet is now, parent bodies of other meteor showers … and Isaac Newton’s Vis-viva equation, his poetic rendition of instantaneous motion.
Bruce McClure has served as lead writer for EarthSky’s popular Tonight pages since 2004. He’s a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.
Published On Earth Sky News
The Wisdom of Buddha
There is nothing more dreadful than the habit of doubt. Doubt separates people. It is a poison that disintegrates friendships and breaks up pleasant relations. It is a thorn that irritates and hurts; it is a sword that kills.
Your Daily Influences for Today
Four of Swords
A period of rest and restoration of energies. Tensions subside. Good changes are soon to come.
Aries reversed denotes a lack of energy and will
Air reversed denotes a lack of freedom to move through life as you want.
Past Lives Tarot for Today
The Hanged Man
A famous artist is a visionary who has captured images of the moment of time they lived in. You are probably also feeling that this is your moment to express what you really have to say and you need to do it visually. Possibly you were an acclaimed artist in a past life and once again their spirit yearns to express itself through you. Open yourself up to this incredible gift and use it wisely.
Daily Love Tarot
A decision works to your advantage if you make it after serious deliberation. As you do the latter, add a touch of intuition. Something that nags at you and nibbles at the edge of your memory has relevance today. Does something need to end? The Universe offers change for your own good when you need it. Closing chapters leads to opening new chapters. Ends are rites of passage just as beginnings are.
Tarot Card of the Day
Three of Fire
This suit, most often called “Wands” and sometimes called “Rods” or “Staves,” represents initiative, ambition, drive and desire. This is the suit of enterprise and risk-taking.
A Three in this suit symbolizes an inner balance that allows you to feel more optimistic about new endeavors you are committed to, or want to commit to. In the illustrated Tarots, the human character is standing on his balcony, watching ships leave the harbor, loaded with his goods for far-off ports, dreaming of the fortune he will reap if all goes well. Summon the optimism within you.
This energy must be patient and trusting, because he or she will have to wait some time to find out how the ships have fared. Meanwhile, a lot of resources are tied up until they return with the bounty. Only those truly confident in their ideas and abilities would undertake such a risk. This card represents the energy a person needs to take on great adventures and accomplish noble (and remunerative) deeds.
A detail that sometimes appears in the more esoteric Tarots is a winged wand with two snakes twining around it, called the Caduceus, which is Mercury’s wand. This is an ancient symbol of the healer or shaman, one who can travel between the worlds to rescue souls from death or possession. Perhaps the feeling of empowerment this card represents points to the internal mechanisms of self-healing. Perhaps it refers to the courage it takes to be an entrepreneur or an inventor, which is in itself a magical process — bringing not only opportunity for success, but also an awakening to higher potentials.
Part of the Daily Insight Group ©2017
Get A Jump on Tomorrow…..
Your Daily Horoscopes for Thursday, May 4th
The Moon moves into your work and health sector this morning, dear Aries, and you can be geared up to get things done. However, you don’t have all the information you need, or you’re waiting for something that never seems to come. Try not to put too much of your energies into tasks that just aren’t ready to move forward or to wait impatiently when your energies can be better used elsewhere. With communications and transportation, be patient as well. Disagreements can be irritating. Taking on too many things at once can lead to unnecessary complications, so aim to keep it simple today.
Crossed wires can easily occur again today, dear Taurus, although if you can tame impatience, you have the rare opportunity to see behind you and ahead of you to consider what’s your next step. Try not to take it to heart if someone says something that seems a little off. Tensions can rise, particularly if you are pulled in different directions or if you want to do a lot more than is possible now. Keep things simple rather than take on more than you can comfortably handle. Don’t feel pressured to make a decision or draw a conclusion now. Pushing these things is unlikely to work to your advantage and can cause undue stress.
With Mercury only just pulling out of a direct station, dear Gemini, you have time to sort things out if you’ll allow things to unfold slowly. However, Mars challenges sluggish Mercury now, and this can produce unnecessary pressure or stress to move forward prematurely. Try not to succumb to this. As well, avoid snap judgments and decisions or hasty communications, particularly with friends and networks. You may be juggling too much, likely personal interests and the needs or demands of a friend, and tension can result if you can’t seem to focus on either one or the other.
Rising tensions tend to come from dividing your attention between two very different drives, dear Cancer. Topics vying for your attention are likely to be personal or private matters, and professional/work-related. Watch for being impatient and short with others if you are juggling a lot. Things may not be moving ahead as quickly as you’d like. Tread lightly when it comes to interactions with others and communications, particularly on professional and public levels. Avoid speaking too fast on a matter. Creative explorations fare well today, however. The Moon’s move into your communications sector this morning keeps you on your toes and connections with friends or a partner can be particularly satisfying.
Emotions tend to settle down, or you’re not treating emotional needs as urgent today, dear Leo, with the Moon’s move out of your sign this morning. However, watch for impulsive communications and movements, whether you’re walking, driving, talking, or texting with Mars and Mercury in minor challenging aspect today. Mercury has just turned direct but is only slowly moving away from a standstill, yet you’re anxious to get somewhere or to make something happen. Tame impatience and avoid communicating too quickly, prematurely, or cuttingly today and tomorrow for best results. This is not the time to push yourself.
The Moon moves into your sign this morning, dear Virgo, and this begins a new lunar cycle of emotional focus. Although on some levels you may feel as if you’re starting fresh, your ruler, Mercury, is just pulling out of a direct station and is connecting in a minor challenging aspect with Mars. This can point to misjudgments as you feel pressure for something to move forward when it’s too early to do so. Watch what you communicate today, particularly regarding how quickly you share an observation or make a criticism. Impatience can lead to irritating and unnecessary conflicts. Aim to accept that you’re not quite ready to push ahead and that problems are unraveling on their own time.
You can feel particularly impatient with conversation today if you want to get moving and doing rather than simply talking about it, dear Libra. However, it’s not yet the time to feel fully on the same page with a significant other. There can be much talk about nothing you actually care to hear about now. If you’re not feeling tense, then you may be attracting people who are grumpy or impatient. The sooner you tune out the nonessential and accept that you may need to wait a little longer for things to get back on track, the better you make use of the day’s energies which are quite excellent for injecting some extra excitement into your routines or work.
While the day is good for expressing your enthusiasm or affections for someone through your actions, gestures, and body language, dear Scorpio, communications over the phone or otherwise not face to face can be misunderstood. There can be anxiousness to get something going, mainly related to work or health endeavors, but pushing forward may not be wise now. Work and tasks can feel rushed yet you don’t have all the information you need to make the big decisions, so aim to pace yourself now. If you center yourself, you can tune into opportunities to connect with a person or project with passion.
While you may have an easy time expressing your affection or interest in someone through your body language and gestures today, dear Sagittarius, there can be some curtness or impatience in our speech that can put a damper on things, most prevalent when communicating with someone from a distance rather than face to face. Restlessness or impatience can disrupt a perfectly good thing today, and it’s important to avoid trying to push for a decision or answer before it’s possible to do so mindfully. The Moon moves to the top of your solar chart this morning, prompting you to review recent performance or goals. However, nervous tension can interfere with your perceptions, so aim to take it easy instead of drawing quick conclusions.
There is good energy for work, dear Capricorn, particularly creatively speaking. However, there can be miscommunications between your actions and thoughts. Doing more than one thing at once can be particularly stressful today since there can be half-heartedness involved with most things. Spreading yourself too thin with your work or health efforts can be less than satisfying. Mercury has turned direct but is still apparently moving slowly as it pulls out of its station, and plans are not rolling forward yet, so have patience for best results now.
Mercury has just turned direct and is slowly moving out of its station in your communications sector, dear Aquarius. This can be a good time for taking a pause and considering your next move. With Mercury’s clash with Mars today, however, you can feel pressured to make a decision or put an idea into motion. Consider that you’re not quite ready to do so. There can be some curtness or apparent insensitivity in communications now if we are impatient in these ways. Try not to divide your attention or attempt to take on too many different topics and interests, as it can quickly lead to unwanted stress and tension.
Try not to succumb to pressures to make a quick decision or to push a plan forward today, dear Pisces. Mercury has only just left its retrograde period but it will be a while before it resumes regular speed, so it’s best to ease yourself into Mercury-related activities, including new ideas and decisions or plans. Try also to avoid dividing your attention so much that you end up stressing yourself out. Keep things simple now. The Moon’s move into your partnership sector this morning can prompt you to seek out companionship for much of what you do. Alternatively, this can be a time for seeing your life through others’ eyes in important ways.
If You Were Born Today, May 3:
Thoughtful and involved, you express yourself well, possess quiet charm, and easily endear yourself to others. You have an artistic bent that is undeniable, and your creative mind can help bring financial success. You are multi-talented and many of you spread yourself over multiple career paths and hobbies as a result. You expect a lot from yourself, and sometimes too much, which can lead to indecisiveness. Famous people born today: Bing Crosby, Sugar Ray Robinson, James Brown, Mary Astor, Christopher Cross.
Your Birthday Year Forecast:
Your birthday occurs around a First Quarter Moon this year, and you are reaching an important turning point in terms of personal growth. You may be more emotional this year, and you should watch for unnecessary conflicts and making hasty decisions as a result. Otherwise, this is a year of great energy, motivation, and growth. You are more ambitious and desirous of action in the year ahead.
Neptune continues to transit sextile to your Sun this year, however, softening and smoothing many of the rough edges. You are gentler, more intuitive, spiritual, and creative with this influence, and others are drawn to these qualities. Your natural ability to help others heal and calm down is enhanced. A higher purpose to your life is what you seek, and you rely more heavily upon your intuition in order to achieve it. You could find that your intuition is subtly enhanced and that you’re often in the right place at the right time, probably because your hunches are more likely to be correct. This aspect softens your disposition somewhat, as you tune into your imaginative and artistic side. This is a good year for self-improvement programs or efforts. The need to “get away from it all” — for some peace and quiet now and again — will be strong. A more sensitive, even mysterious, persona is projected this year, and this can attract pleasantly unusual circumstances (and people) into your life. You will want to spend more time away from chaotic situations.
Helping you with the practical side of life is a Mercury-Saturn connection. Your thinking is often practical and realistic, and your judgment is especially sound. You also derive much satisfaction from practical achievement. It would behoove you to identify and focus on finding pleasure in the simple things that make you happy.
Advances in intellectual and mental pursuits are likely, as you make steady progress that has long-lasting results. It’s a good year in which to get organized, to do detail work, and to prepare for the future. Work done during this period in your life will have tangible results in the future. Relationships with younger people in your life are solidified.
This can be a good time for updating your electronics and technology in ways that open up new avenues for communication or ease. Wonderfully creative ideas can fill your head this year.
There can be a stronger focus on loyalty in your relationships, and working relationships can improve or work with a partner can be in focus.
This is a year of both practical application and an imaginative approach. This can be a time of career advances and is a strong period for focusing on priorities. However, it’s also a period for projecting a warmer, softer image and for building your creativity and imagination or discovering a spiritual side.
2017 is a Number Nine year for you. Ruled by Mars. This is a year of completion and transition. It is a time when we need to let go of things that no longer serve their purpose, and hold on to things that have a future. It is a time of cleaning out dead wood, not necessarily for new beginnings. It can be a time when a burden has been taken off your shoulders, and it can be a year of giving of yourself. Advice – let go of things that are holding you back, give of yourself and express your sympathetic, compassionate side.
2018 will be a Number One year for you. Ruled by the Sun. This is a year of action. The seeds you plant now, you will reap later. Others might find you less sociable, as you are busier than ever and you focus on your activities and your needs. Still, you are outgoing and your initiative is stronger than ever. Advice – Stand alone, take action, start fresh, express independence.