What is rigels right ascension

Rigel belongs to spectral class B8 and has a luminosity class of I corresponding to a supergiant star. The red dot in the diagram below shows where Rigel is situated in the Hertzsprung—Russell diagram. H-R diagram showing the position of Rigel. The table below shows key information about the Rigel double sysyem:. This site cannot run without your voluntary donations.

We don't use Ads. If you find this website useful please consider a small donation, it will help covering hosting costs. Rigel is a blue supergiant that is the brightest star in the constellation Orion the Hunter. Due to its measured size and brightness it is expected to end in a supernova one day.

It also has two known companions, Rigel B and Rigel C. The star is about light-years from the sun and 47, times as luminous, according to Encyclopedia Britannica. It is a variable star its apparent brightness varies and is considered an Alpha Cygni-type star. Alpha Cygni is the scientific name for Deneb, the prototype star for this kind of brightness variability.

Rigel's name is popular in science-fiction. A fainter star much farther from Rigel might also be a component. The secondary star is referred to as Rigel B.

The angular rotation of Rigel B from Rigel A is 9. It has a visual magnitude of 6. Though, both stars appear to share the same proper motion. The pair would have a minimum orbital period of around The next companion is named Rigel C. They have a measured separation from component B that varies from less than 0. Recent observations showed the two identical components separated by 0.

Their estimated orbital period is 63 years. The two spectroscopic components Rigel Ba and Rigel Bb cannot be resolved in optical telescopes but are known to be hot stars of spectral type around B9.

This spectroscopic binary, together with the close visual component Rigel C, is likely a physical triple star system, although Rigel C cannot be detected in the spectrum which is inconsistent with its observed brightness. Rigel C is estimated to have around 3. The fourth companion of Rigel, named Rigel D is still disputed to be part of the system.

In , its separation from Rigel was Gaia DR2 finds it to be a 12th magnitude sun-like star at approximately the same distance as Rigel. Likely an orange dwarf, this star would have an orbital period of around , years, if it is part of the Rigel system. Since we're inside a sphere, it would continue around the backside of the Earth as well. From mid-latitudes, the celestial equator stands midway between the horizon and overhead point, while from the poles the celestial equator encircles the horizon.

Anything north of the celestial equator has a northerly declination, marked with a positive sign. Anything south of the equator has a negative declination written with a negative sign.

One star is north of the celestial equator and the other south. Can you guess the declination of the north celestial pole? While we use a physical location on Earth as our reference for longitude, what reference do we use for right ascension? Astronomers use the spot the Sun arrives at on the first day of spring, called the vernal equinox.

Presently, it's located in the constellation of Pisces, the Fish. The sky can be treated as a clock, since it wheels by as Earth rotates, so the zero point of right ascension is called "0 h " for "zero hours. That's a little more than one-half the width of the W -shaped constellation Cassiopeia. In keeping with right ascension's time theme, hours are subdivided into minutes and seconds, and are even written out as minutes m and seconds s.

Let take the North Star for example. Polaris is located at RA 2 h 41 m 39 s , Dec. Because the stars circle about the sky every 24 hours, right ascension or RA ranges from 0 h to 24 h. Unlike Earth coordinates, celestial coordinates change due to the slow wobble of Earth's axis called precession.

Precession causes the equinox points to drift westward at a rate of As the equinox shifts, it drags the coordinate grid with it. That's why star catalogs and software programs have to be updated regularly to the latest "epoch.

Most catalogs and software currently use Epoch J The next major update will happen in Learning RA and Dec. Before computer software effortlessly plotted the paths of newly discovered comets and fast-moving asteroids, I couldn't wait to get my hands on their coordinates. I'd hand-plot the positions on a paper star atlas, then swing my scope to the spot, and thrill when I found it on my own. RA and Dec. Just input its coordinates, hit enter, and you're there. If you hear of a new comet or fast-moving asteroid, a quick check of its changing coordinates will tell you not only where it is but where it's headed, so you can plan the best time to see it.

I made friends with right ascension and declination long ago. Knowing I could drive anywhere on its invisible roadways helped me, and it'll help you too become more familiar with the night sky. Good review and I enjoy RA and Dec. Much of my observing is with a Telrad. You can convert RA and Dec. Log in to Reply. Bob King said: I'd hand-plot the positions on a paper star atlas, then swing my scope to the spot, and thrill when I found it on my own. I don't know how to take this step with my Dobsonian.

Do I need some add on protractor etc? How do I find the vernal eqinox? Not much sky watching this winter. Stew Shouldice. Bob King Post Author. Hi Stew, I also use a Dob and have for many years. You don't need to know where the vernal equinox is if you're hand-plotting. You get the specific RA and Dec.

If it's a bright star, then that's easy, you look to see if that star is up in the sky at the time you want to view it. You can do that by using a planisphere star-wheel or a free software planetarium program like Stellarium. If you're looking for a fainter object, you'll need a star atlas. Star atlases will always shows right ascension along the bottom and declination along the side. You locate a specific object by interpolating between those numbers. Larger atlases come with their own separate fine-gradation grids you can place over the page to really nail the position down.

Does this help?