Weekend Sky Report / Rho Cassiopeiae
August 16, 2019
Rho Cassiopeiae (row casio-pee-eye) is huge. More than 400 times the size of the sun and 40 times as massive. And did I mention it’s bright? Half a million times brighter. Now it’s by no means the MOST luminous star we’ve ever found, but it is one of the brightest yellow stars. Yellow stars, or Class-G stars are fairly common. Our own sun is a Class G. But Rho Cassiopeiae is a yellow hypergiant--a particularly rare and short-lived type of class-G star. They’re thought to be a type of star that evolves from a red supergiant to a hotter blue star. A strange evolution indeed in the celestial world. So even though we’ve known about this particular star for centuries, this huge, bright, yellow stage in its evolution is relatively brief. Strangely massive stars like this have short lives. Rho Cassiopeiae is probably no more than 6 million years old.
To find it, find Caph--the second-brightest star in Cassiopeia. It’s also the highest star in the constellation in our current evening sky--and the one furthest to the right if you were to turn Cassiopeia on its side so it looks like a W. From Caph, scan to the right and up with a telescope or a decent set of binoculars until you see a yellow star. Consult a star chart to make sure you have the right one.
Of the hundreds of billions of stars in the Milky Way, we’ve only found a dozen yellow hypergiants like Rho Cassiopeiae. So if you see it, you’ll be looking at one of the rarest star types we’ve ever discovered.
May 22, 2020
Some amateur astronomers in the northern hemisphere say that Spring is galaxy season. Basically what that means is that the Virgo Cluster is high in the evening sky.
May 15, 2020
To the West, the last remnant of the Winter Triangle. To the East, the first stellar sign of the coming summer.
May 08, 2020
We're halfway through Spring. A perfect time to look for what some call the "Great Diamond."
May 01, 2020
When the moon is out, it's hard to see dimmer stars and deep sky objects. But there's still plenty to appreciate about our natural satellite.
Apr 24, 2020
Messier 3 is a remarkable globular cluster. It's over 33,000 light years away, but it's bright enough to see with a small telescope, which means it's dense. Around half a million stars exist there.
Apr 17, 2020
The Lyrids are active all weekend, so you may see some tonight under dark skies, but the big peak comes early this coming Wednesday morning April 22, 2020. This year we're expecting 10 to 15 meteors per hour.
Apr 10, 2020
To find Gemini, look to the west and find the familiar Orion. You'll know it by its iconic "Belt" of three bright stars in a row. Then, simply look above Orion for two bright stars next to each other.
Apr 03, 2020
As Venus continues its rise in the evening sky through the end of April, it will travel through many constellations. Tonight, Friday, April 3rd, it will be in the middle of the Pleiades star cluster.
Mar 27, 2020
If we're lucky enough to get clear skies in the early morning--before 7am Eastern, look to the south and you'll see three bright points of light. From left-to-right, it's Saturn, Mars, and Jupiter.
Mar 20, 2020
The Beehive Cluster is right smack in the middle of Cancer the Crab, which is actually a very dim constellation.
Mar 13, 2020
Blue stars that are really close to red stars can appear to us as a greenish blue. One good example is Antares B, the binary companion to the red giant Antares A, the heart of Scorpius.
Feb 28, 2020
Leo sweeps across the southern sky all night this time of year. In the evening, it's to the east. To find it, look for the Big Dipper. It'll be straight up and down with the cup at the top. Connect the two stars at the top that make up the end of the cup, and from that straight line, extend the line to the right toward the east, and when you hit the bright star Regulus, you've arrived.
Feb 21, 2020
Every good hunter needs support. Orion and his two dogs have reigned the evening sky in the winter since before human civilization. One of the earliest representations of Orion appeared in cave art dated more than 32,000 years ago.
Feb 14, 2020
On Tuesday morning, February 18, 2020, just after 7am Eastern, Mars will disappear behind the moon. An event known as a lunar occultation.
Feb 07, 2020
Sirius is a binary system consisting of the very bright, main sequence stage star we can see with the naked eye, Sirius A, and a much smaller companion white dwarf stage star, Sirius B.
Jan 31, 2020
Venus is 15 times brighter than the brightest star in the night sky, Sirius. And planets don't twinkle like stars do.
Jan 24, 2020
The Triangulum Galaxy gets its name from the constellation where it's found. It's a small constellation and, as the name suggests... it's a triangle.
Jan 17, 2020
The Orion Nebula is just over 1300 light years from our solar system, and it's believed to be an enormous 24 light years across. Because it's so big, and... relatively close, it's easily visible with binoculars or a telescope, even under fairly bright, suburban skies.