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exotic

September / October

RA 00 - 04

Finder charts for all September/October objects as pdf file

Finder charts for ALL exotic objects as pdf file

Adam Block/Mount Lemmon SkyCenter/University of Arizona

VdB 1 and V633/V376 Cas

A reflection nebula and two YSOs in Cassiopeia

00 10 46.37 +58 46 10.3 (VdB 1)

 

Van den Bergh 1 not only is the number one in the VdB catalog, it is also one of its more rewarding targets. VdB 1 is relatively easy to find SE of beta Cas, the westernmost star in the "W" of Cassiopeia. The reflection nebula appears relatively bright around a group of stars and reveals a slightly striated structure.

NE of VdB 1, a dark cloud is relatively obvious and at its NE edge are two young stars (Young Stellar Objects, YSOs). V633 Cas (PP2) is the brigher of the two and appears at first sight stellar. At higher power, a diffuse shell can be discerned around the star, that extends somewhat towards SE. The annular structure visible in the image to the left was not visible. V376 Cas (PP3) is considerably fainter and can be seen only using indirect vision without further structure.

These nebula are reflection nebula and should not be confused with the Herbig-Haro objects HH161, HH162, and HH164, which are as well associated with these young stars, but visually not accessible.

 

The lower image of this area was taken by Adam Block and shows fantastic structural detail of the two YSOs.

 

More about Young Stellar Objects is here.

 

star forming regions in IC 10

Phil Massey, Lowell Observatory

IC 10

A dwarf galaxy with HII regions in Cassiopeia

00 20 17.34 +59 18 13.6

 

IC 10 is only one degree further towards E and belongs as one of the brighter dwarf galaxies of our Local Group to the Andromeda Galaxy. IC 10 is a relatively young star burst galaxy with very active star formation.

IC 10 is an observing target intermediate between the two brightest companions of the Andromeda Galaxy, NGC 185 and 147, and the fainter dwarf galaxies IC 1613 or WLM. At the eyepiece, it appears under fair conditions as a faint, but distinct elongated patch, well above the sky background.

The lower image reveals a number of HII regions in this galaxy of which some are within reach for visual observation. The southern part of the galaxy appears much better defined as compared with its northern end, which is comprehensible from the image. Even without any filters, this part of the galaxy appears structured, which is due to one of the brighter star forming regions. With UHC or OIII filter, these regions can be identified more clearly. The effect of the filter is, however, not that pronounced, as the light of the young intense stars in these HII regions gets blocked.

Interestingly, under light polluted skies, the brightest of the these HII regions may be even more distinct than the galaxy itself. During an observing session with a limiting magnitude of only 5.5, the star forming region was distinct, while the galaxy itself remained very vague only.

 

NGC 185 and NGC 147

Two dwarf galaxies in Cassiopeia

00 38 57.97 +48 20 14.6 und 00 33 12.12 +48 30 31.5

 

These two galaxies are companions to the Andromeda Galaxy and have, typical for most dwarf galaxies, an only low surface brightness. It is, however, still much higher than all other companions of M31 or our own galaxy, with the exception of the Magellanic Clouds.

NGC 185 is somewhat easier to observe than NGC 147 and appears more condensed, despite having approximately similar size. A challenging target is a dark lane NW of the center of NGC 185.

 

NGC 253 and NGC 247

Two big galaxies deep south in the Sculptor Group

 

NGC 253 (00h 47, -25 17') bears as the "Sculptor Galaxy" even the name of the galaxy cluster and the name of its constellation, being  the central galaxy of the Sculptor Group. With a brightness of mag 7, it extends over half a degree and is despite its position only slightly above the horizon (at my 48 N latitude) a conspicuous object. Under optimal transparency and with a large Dob, however, it becomes a fascinating object and easily steals the show from even M31. In contrast to the Andromeda Galaxy, NGC 253 is highly structured with several dust lanes and knots and appears as an almost three-dimensional whirlpool. At the eyepiece, its appearance is comparable then to the DSS image to the left. Classified as an SABc galaxy, it is a widely opened spiral with a small central bar, which is, however, hard to see due to foreshortening.

 

NGC 247 (00h 47, -20 46') has a length of 21' and is therefore only slightly smaller than NGC 253. NGC 247 lacks all those features where NGC 253 excels. Not only is it at mag 8.9 more than one and a half magnitude fainter. It also lacks pronounced internal structure. Even with my 22" Dob, NGC 247 appears as a ghostly elongated streak with no details except for a condensation towards the middle. A mag 9 star at its southern end gives the impression of the galaxy being hooked to it. At my 48 northern latitude, the galaxy disappears easily under hazy conditions due to its location close to the horizon (despite being even 4.5 farther north than NGC 253). The chain of background galaxies visible in the image NE of the galaxy is known as Burbidge's Chain and a challenge for larger telescopes.

 

NGC 383 and Friends

A galaxy group in Pisces

01 07 24.94    +32 24 45.2

 

NGC 383 is a mag 12 galaxy and stands in the middle of an impressive chain of other mag 12 and 13 galaxies, as well as a fair number of fainter ones. Due to its brightness, this group is a rewarding target also for small and medium-sized telescopes.

This galaxy group is at a distance of approximately 220 million LYs and belongs to the Pisces-Perseus super cluster.

 

NGC 507 and Friends

... and another galaxy group in Pisces

01 23 40.00 +33 15 20.0

 

This group is just around the corner of the NGC 383 group. NGC 507 is a giant elliptical galaxy with a brightness of mag 11.2. It is surrrounded by seven more galaxies brighter than mag 13.0 and much more that are fainter. The NGC 507 group is therefore similarly as the NGC 383 group a rewarding target also for smaller scopes. Wtih my 14" Dob, 15 galaxies were visible without problem. Compared to the 383 group, the 507 group appears a bit more difficult, despite that the member galaxies have similar magnitudes. This is probably due to the larger number of bright foreground stars in the immediate vicinity, making it a bit more difficult to identify the galaxies.

This galaxy group is at a distance of about 200 million LYs and belongs as well to the Pisces-Perseus super cluster.

 

A large finder chart is here.

 

Simeis 22

An old and giant PN in Cassiopeia

01 30 40 +58 22 00

 

Simeis 22 belongs to the apparently largest planetary nebula and is one of the brighter ones of the illustrious list of the large PN. Its diameter is 10' and, with OIII filter, it appears as a large crescent-shaped brightening, so to say a dimmer version of the Medusa Nebula, Abell 21. In contrast to Abell 21, the crescent does not appear closed visually. Under very good conditions, single filaments are at the edge of detection, giving the PN a somewhat striated appearance.

 

More about large PN is here.

 

Heart Nebula

A huge nebula complex around Melotte 15 in Cassiopeia

02 32 42    +61 27 00

 

The Heart Nebula is a huge HII region just north of the h/chi Double Cluster, consisting of several single nebula. It responds well to all nebula filter (UHC, OIII, H beta) with a slight advantage to the OIII filter.

The brightest region is the north-western part, comprising NGC 896 and IC 1795 as a smaller bright one and a larger, somewhat fainter patch. Panning towards SE leads to the distinct open cluster Melotte 15, which is in the heart of the Heart and will be our starting point for further exploration.

Mel 15 is surrounded by nebulosity which bears the designation IC 1805. This part extends from Mel 15 somewhat towards E. Besides this central part, there are other regions of interest: A quite distinct arc passes the cluster on its north side. Another one passes more distant on its southern side, becomes  SE of the cluster fainter, turns then towards north and becomes again more distinct. A third stretch of nebulosity extends straight from the eastern part of the central IC 1805 towards NE and can be followed over a quite large distance with filter.

 

East of the Heart Nebula is another large HII area, IC 1848, that is divided into two parts and that bears the name Embryo or Soul Nebula. This nebula is also well accessible with OIII filter.

 

Maffei 1

A close elliptic galaxy in the dust of the Milky Way in Cassiopeia

02 36 35 +59 39 19

 

Maffei 1 is a huge elliptic galaxy just beyond our Local Group and belonging to the IC 342/Maffei Group. Maffei 1 were one of the brightest galaxies in our sky, if, yes, if it were not positioned from our view point behind the plane of our Milky Way. The dust in our galactic plane attenuates the light from Maffei 1 to only 1/120, corresponding to a dimming by 5 magnitudes.

At the telescope, Maffei 1 appears as a faint oval brightening without further structure. Superimposed onto the galaxy is the unimpressive and loose open cluster Czernik 11.

About 1 degree east is Maffei 2, a similarly dimmed spiral galaxy, which is, however, considerably more difficult than Maffei 1.

 

Image by Geert Vandenbulcke

Merope Nebula and Barnard's Nebula

Two superimposed reflection nebula in the Pleiades

03 46 19.57 +23 56 54.1 (Merope)

 

Merope Nebula (NGC 1435) is the brightest one of the reflection nebula in the Pleiades. Under good conditions, it is visible even in large binoculars as a faint fan-shaped smudge, extending from Merope outward of the cluster. Merope Nebula is one of those objects that can be hard to observe for the first time and that become relatively easy once you know what to look for.

These reflection nebula are actually not remainders of the molecular cloud in which the open cluster initially formed. Rather, they originate from denser parts of interstellar matter, through which the cluster presently happens to pass through. The visibility of the Merope Nebula is a good criterion to judge the quality of your sky.

Superimposed on the large Merope Nebula is a much smaller one, Barnard's Nebula (IC 349), which is brighter, but very close to Merope, extending only 30" from it. IC 349 is considerably more difficult than the Merope Nebula and not just visible at first sight. Instead, it requires a lot of patience to successfully observe it.

When I observed it for the first time, I used a 6mm eyepiece equipped with a strip of black slide film at the field stop. This allows placing Merope behind that strip and to suppress its glare (this is actually the same equipment that I use for Sirius B). With a lot of patience, a small appendix to Merope could be made out. Its orientation could be noted using the surrounding small field stars and later be verified using photographs of this object. Barnard's Nebula has a diameter of only 30"  and is nicely resolved in the image by Geert Vandenbulcke (left). The HST inset further reveals the bizarre structure of IC 349, caused by dust filaments eroded by the radiation pressure of Merope.

 

finder chart as pdf

Uranus and its moons Puck, Miranda, Ariel, Umbriel, Titania, and Oberon (NASA)

Neptune and Triton (Voyager mission, NASA)

The satellites of outer planets

Observing the moons of Uranus and Neptune

 

While the planetary disks of Uranus and Neptune hardly show any interesting detail, already medium sized telescopes show satellites of these two outer planets. The main difficulty consists of resolving their faint dots next to the relatively bright planetary disks using indirect vision.

 

Uranus has a peak brightness of 5m6 and a maximum diameter of its disk of 3.6". Its brightest moons are from inside to outside (with peak brightness and diameter)

Miranda at 16m5 (472 km)

Ariel at 14m4 (1158 km)

Umbriel at 15m0 (1169 km)

Titania at 13m9 (1578 km)

Oberon at 14m1 (1523 km)

Presently, I have succeeded in observing repeatedly Titania, Oberon, Umbriel and Ariel. The moons of Uranus are relatively small, their overall mass being less than half of the mass of Triton, the largest satellite of Neptune.

 

Neptune has a maximal brightness of 7m8 and a maximal diameter of its disk of 2.5". The only satellite within reach of amateur telescopes is Triton. All other moons are mag 19 or fainter.

Triton at 13m4 (2700 km)

Triton revolves Neptune in a little less than 6 days with an orbit inclined by 157 compared to the ecliptic. At present, we have a polar view of this planetary system, such that Triton is always at sufficient distance from the planet. Due to its brightness, it is even easier to observe than any of the moons of Uranus. Despite being more distant than the moons of Uranus, Triton is brighter. This is due to two reasons: Its diameter is almost twice as large as that of the larger Uranus satellites; and Triton has a comparatively large albedo of 0.76 hinting at a bright ice surface, while the typical albedo of the Uranus satellites is only half of that.

For comparison: Titan, the largest moon in Saturn's system has a diameter of 5150 km and a brightness of up to 8m4, while Ganymede, the brightest and largest satellite in Jupiter's system, measures even 5262 km with a peak brightness of 4m6. Our familiar Moon, on the other side, measures only 3476 km.

 

image credit: DSS

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