Look southward at dusk and nightfall, and you can’t miss Sirius, the brightest star in the nighttime sky. Only the planets Venus and Jupiter are brighter, but they’re in the western sky. The waxing crescent moon will join these planets in the western sky beginning around March 23.
Venus and Jupiter are temporary visitors to our sky at this time of year, whereas Sirius is a permanent fixture of March skies. Mia asks, “Isn’t there a brighter star in absolute magnitude which appears dimmer because of its distance?”
March 2012 guide to the five visible planets
Catch the young moon, Venus and Jupiter after sunset beginning March 23
Image Credit: Yuuji Kitahara
Yes, Mia, you are right. Sirius, in the constellation Canis Major (the Greater Dog), looks extraordinarily bright in Earth’s sky because it’s only 8.6 light-years away. Many stars on the sky’s dome are intrinsically more luminous than Sirius but appear fainter because they lie farther away.
At least three stars in Canis Major are thought to be thousands of times more luminous than Sirius: Aludra, Wezen, and Omicron 2. Although the distances to these faraway stars are not known with precision, Aludra and Omicron 2 reside an estimated 3,000 light-years distant, and Wezen at about 2,000 light-years.
To get a better idea of a star’s true luminosity, astronomers like to list stars according to “absolute magnitude.” Absolute magnitude measures the brightness of the stars as if they were all an equal 32.6 light-years distant.
If you're not sure the bright star you're seeing is Sirius, remember ... Orion's Belt always points to Sirius.
At 32.6 light-years away, our sun would barely be visible as a speck of light. In stark contrast, Aludra, Wezen, and Omicron 2 at 32.6 light-years distance would outshine Sirius (at its distance of 8.6 light-years) by some one to two hundred times. At 32.6 light-years, Sirius would be about the same brightness as the Gemini star Castor. So if all these stars were equally distant, these super-luminous stars in Canis Major would shine thousands of times more brilliantly than Sirius.
Once again, absolute visual magnitude measures the star’s brightness as it would appear to the eye at 32.6 light-years away. Apparent visual magnitude refers to a star’s brightness as seen by the eye from Earth.
Bottom line: Sirius is our sky’s brightest star (although not as bright as the planets Venus and Jupiter, now in the west after sunset), but not the most luminous star in the sky. In other words, it’s an ordinary star that only appears bright to us because it is relatively nearby.
The Stellar Magnitude System by Alan M. MacRobert
first time on the site and was wondering what those two bright stars in the west were. im in oklahoma, usa. and know very little about the nite sky . these show up good at my house toward 8 – 10 pm
Rick,
Those two bright lights in the western evening sky are the planets Venus and Jupiter, with Venus being the brighter of the two.
Bruce
Yep – Venus and Jupiter – pretty amazing sight even thru my puny Celestron 80 9MM w/ Barlow 2x – Jupiter’s cloud bands and moons visible – sweet!
I’m located just north of Boston. Last nite, 3/20, stepped outside at 11:00 and noticed in the SW sky what I assumed was a plane approching Logan Airport. With naked eye it appeared to change from white to green to reddish. After seeing that it wasn’t moving I viewed with binoculars and saw it was changing color. I got out my telescope which is not very strong and it appeared to be almost a flattened diamond shape that was pulsing color. What was I looking at? Thank you
Dennis,
That was the star Sirius. This star appears in the southern sky at dusk and early evening, and drifts westward as evening deepens into late night. It finally sets in the southwest sky around midnight. When a brilliant star hovers near the horizon, the extra-thickness of the Earth’s atmosphere acts like a prism, breaking up the starlight into the flickering colors of the rainbow.
Bruce
thanks.
Thank you Bruce. I’m a total novice and had never seen a pulsing star like that.
I live in East Devon.South West England.We have had a fantastic view of the Planets,Venus,Jupiter and Mars.I`ts amazing to see.
goodbye.
Can you confirm that Saturn is rising in the eastern sky in the late evening please ? It seems to sparkle in my quality binoculars . Mars Venus and Jupiter are very easy to identify but Saturn is mysterious ! UK north of BIRMINGHAM .
Martin,
Yes, Saturn is rising in the east to southeast at middle to late evening, well before the planets Jupiter and Saturn set. Saturn shines fairly close to the constellation Virgo’s brightest star, Spica. Saturn looks golden through binoculars while Spica sparkles blue-white. It’s my guess that you were looking at Spica, not Saturn.
Bruce
Amazing website! I’m a novice when it comes to the night sky, but I’m starting to really get into it. Off to the fields with the dog now, we have a very clear sky here in central Scotland. Happy stargazing :-)
If Venus and Jupiter are not in the Western sky until the 23rd, what are the two bright stars I’ve seen there for weeks?
They are Jupiter and Venus – you are confusing with the waxing moon !
Phil,
It’s the waxing crescent moon that won’t join up with Jupiter and Venus in the western sky until March 23.
Bruce
Just walked up the road and seen Venus WOW!
I took my children, aged 13 and 11, out for a walk before bed this evening, mainly to see Jupiter and Venus. We live in a small town and the light pollution made it quite tricky to see much else, even from the outskirts. Still, it proved a very enjoyable and educational stroll. I am looking forward to using some of the daily items as challenges for them on our walks though they’ll need to be the naked eye or binocular suited ones :-) Many thanks for such an informative site.
Checking out Venus, Jupiter and Mars on the south side of Chicago at dusk time. Very cool!!!
Finally found out what that bright star in the southern sky was. I told my 90 year old father-in -law about Venus and Jupiter last week end. He goes out every night now to check them out.
yea i can see it here in Canada in the west sky i thought it was a UFO lol but my girl told me to go google it b4 i start thinking crazy shit anyway cool site thx 4 the info
So much for the stars tonight: the fog has rolled in here.
Wow! My new telescop arrived today…I was goin to ask what those two planets were but I now know! This is amazing!
Thank you so much everyone for all the info. I live near Cleveland Ohio and its about 70 out and a beautiful clear sky!!! I also was wondering about the two bright stars in the west. Thanks so much everyone!
Michelle, those aren’t stars…the big one is Venus and the smaller one is Jupiter. If u look back to the east, the red planet Mars is visible…
My husband saw a big shooting star this morning, at 6:18 a.m. 3-21-12. Another friend saw one this evening around 8 p.m. We live in Northeast Ohio. Anything worthwhile going on? Thanks.
My neighbor and I saw it too this am at the same time. It looked way too big for a shooting star and. Seemed to be glowing a greenish color like it was was on fire hitting the earths atmosphere or something. Moving slower than a shooting star . We live in western Michigan 1 mile from lake Michigan
what were those two bright light last week that I notice in the night sky….each night look as though they were getting closer to each other. I realize one of them probably was Jupiter. What was the other?
Constance,
Those two worlds in the west at evening are Venus and Jupiter, with Venus being the brighter of the two.
Bruce
Forgive me, I forgot to mention that I am in Dutchess County , New York………Constance…..
I’m looking east here in south central Connecticut and see a bright star at maybe 28 el, that literally looks like it’s flashing green and red. With binoculars you can see little flashes and with the naked eye just a little of the twinkling. My iphone app(Goskywatch) seems to indicate it’s in the location of Arcturus. Does that make sense?
Lucinda,
Are you familiar with the Big Dipper? Extending the arc of the Big Dipper handle shows you Arcturus every time. See http://earthsky.org/tonight/follow-the-arc-to-arcturus
Bruce
Thank you–Then, I think it was Arcturus all right! It was so shimmery!
I can see a star that is flashing like crazy red white and blue. It is not to low on the horizon. I think, anyway because it is right above the three story building across the street. It looks like a tiny disco in the sky. I googled “Is there a star exploding right now?” It is sooooo flashy.
Are this planets like Venus and Jupiter in western sky(Canada) always so big and bright around this time or it varies?
Irka
Irka,
It’s special to March 2012.
Bruce
Here in Irvine CA, about 1 mile from the Pacific — I thought it was a space station — thank goodness for this Web site I now have information — they are strangely beautiful, changing shape and colors — awesome!
Thanks for the knowledge! I guessed it was a star — or a planet???? The sky here in Newport Beach, CA is clear and those lights are sparkling and beautiful! What a puzzle, until I found this site.
Love the website. Came looking for information because I had seen the two planets for several nights and wasn’t sure which ones I was seeing.
I live in Jersey and assuming the larger of the two is Venus? Took some photos of the pair and got one that, for a novice, is very cool. You can even see some kind of dark spot — which raises the question of which one I’m looking at!
thanks for the reply from bruce and joe and others about the western sky showing the two planets . is there a good magazine or book you could recommend for a novice like me to learn more about the stars and planets etc.? thanks ,rick
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don’t know