Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

Snow White and the seven dwarfs

Replace Happy and Doc with the seven dwarfs of the sky.
OMearaStephen
This month, I’m challenging you to go after some diminutive objects that spice up the night sky with their hidden beauty. I have selected seven dwarf objects you can search for.

First up is the white dwarf central star of planetary nebula IC 2149, in the northern part of the constellation Auriga the Charioteer. Lying just 40' west-northwest of Pi (π) Aurigae, IC 2149 is an “inside out” planetary nebula. Visually, planetaries usually appear as gaseous rings or butterflies with nearly impossible-to-spot central stars. But IC 2149 is a planetary nebula with a magnitude 11.3 central star surrounded by a tiny and almost inconspicuous nebula 8.5" in extent.

You’ll find our next target, newly designated dwarf planet 1 Ceres, in the northeastern part of Cancer the Crab. Ceres reached perihelion April 22, when it shined at magnitude 7.8 and sailed about 1° northeast of Iota (ι) Cancri. On May 1, the minor world is within 30' of the magnitude 6.7 star 70 Cancri. It then heads southeast toward magnitude 4.5 Kappa (κ) Leonis on the 15th, and about 1° northwest of magnitude 4.3 Lambda (λ) Leonis on the 31st.

The dwarf spheroidal galaxy Leo I appears as a magnitude 10 glow only 20' north of Regulus (Alpha [α] Leonis), the Lion’s brightest star. Glare from the luminary hampers the view. Doubling the difficulty, the galaxy’s light covers an area measuring 12' by 9', so a dark sky and moderate magnification are required. At a distance of 800,000 light-years, Leo I may be the farthest satellite system orbiting our galaxy.

ASYOM0518_01copy
The trick to observing Leo I (top) is to move the brilliant blue star Regulus just outside the field of view of your eyepiece.
Bernhard Hubl
We now proceed to an enigmatic object: the dwarf nova TV Corvi (Tombaugh’s star). Lowell Observatory astronomer and discoverer of Pluto Clyde Tombaugh found this star on plates he took in 1931, during his trans-Neptunian planet search. He considered it a nova. Not until Astronomy contributing editor David Levy researched Tombaugh’s discovery in 1989 did we learn that it has repeated outbursts.

TV Corvi, in fact, appears to be composed of two dwarf objects: a white dwarf and a substellar brown dwarf donor. The variable is characterized by the appearance of long and bright “super-outbursts” that can last weeks. At minimum, TV Corvi lies dormant at 19th magnitude before an outburst brightens it 250 times to 13th magnitude (or brighter) in roughly two days, making it visible in backyard telescopes. You can plot a finder chart at tinyurl.com/y8o8ee2y.

Our next target, magnitude 7.5 Lalande 21185 in Ursa Major (R.A. 11h03m, Dec. 35°58'), is the brightest red dwarf star north of the celestial equator and the third brightest in the entire sky. A mere 8.3 light-years distant, it sails through the background stars at nearly 5" a year.

Red dwarfs are the smallest stars in our galaxy. Lalande 21185 possesses only about half the Sun’s mass and spans only about 40 percent of its diameter. It appears red because the star has a cool surface temperature of 6,400° Fahrenheit (3,800 kelvins). In 2017, astronomers discovered an exoplanet orbiting Lalande 21185. They christened it Lalande 21185b. It is several times larger than Earth, but several times smaller than Neptune.

ASYOM0518_02copy
The Small Cluster Nebula (NGC 7129) combines a star cluster with three nebulous regions. A 6-inch telescope will reveal the cluster. To spot the nebulae, move up to at least a 10-inch scope.
Ken Crawford
Sailing northward along the Milky Way into the constellation Cepheus the King, we encounter a cosmic rosebud, NGC 7129 — a dwarf nebula (with a diameter less than 10' when photographed through a blue filter) 2.6° northwest of magnitude 4.5 Xi (ξ) Cephei, the heart of the celestial king. This evolved HII (star-forming) region belongs to a complex molecular cloud some 3,300 light-years distant that skirts the upper regions of the Cepheus Bubble — a giant dust ring with an apparent diameter of about 10°. NGC 7129 is itself a little bubble of hot gas created by the three B stars within its cavity. Visually the 7'-by-7' nebulosity centers on a trapezoid of stars, which causes the nebula to appear patchy.

As star expert Jim Kaler tells us in his online column Stars of the Week, “Rare is the naked-eye star that has a luminosity and mass less than that of the Sun.” But with a magnitude of 4.5, the yellow/orange dwarf star Xi Boötis can be spied under a dark sky without effort. You’ll find it nearly a fist-width due east of the orange giant star Arcturus (Alpha Boötis). I call it “yellow/orange” because Xi is an easily accessible double star (at a distance of about 22 light-years, one of the closest to our Sun) consisting of a magnitude 4.6 yellow dwarf and a magnitude 6.8 orange dwarf companion some 7" away. So you get two dwarfs for the price of one!

I’ll finish with Snow White. Well, actually, you’ve probably already seen her — the Milky Way. Astronomers investigating the color of our galaxy used Sloan Digital Sky Survey data collected on hundreds of galaxies resembling ours and found its color resembles that of freshly fallen snow seen about an hour after dawn. So, it seems the Milky Way is aptly named.

As always, let me know how you fare by sending emails to sjomeara31@gmail.com.

0

JOIN THE DISCUSSION

Read and share your comments on this article
Comment on this article
Want to leave a comment?
Only registered members of Astronomy.com are allowed to comment on this article. Registration is FREE and only takes a couple minutes.

Login or Register now.
0 comments
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. View our Privacy Policy.

ADVERTISEMENT
ADVERTISEMENT
Apollo_RightRail

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook